Carbonate dissolution on the Muir Seamount (western North Atlantic); interglacial/glacial changes

Using 14 cores changes in carbonate dissolution were examined over the last 125,000 years. The core depth range spans more than 3000 m insuring that major changes in dissolution will be recorded. Weight percent carbonate was plotted as a function of water depth. During the Holocene, the lysocline is located between 4050 m and 4350 m; the CCD is not present even in the deepest sample (4980 m). The late glacial ( approximately 18,000 years B.P.) lysocline may have shoaled to about 2500 m, whereas during early glacial time ( approximately 72,000 B.P.) it deepened to about 3400 m. The mid-glacial carbonate maximum ( approximately 60,000 years B.P.; interstadial?) is marked by a deepening of the lysocline to about 3800 m. During the entire glacial episode, the CCD appears to have remained fixed at 4650 m. The last interglacial ( approximately 125,000 years B.P.) was a time favorable to carbonate preservation; the lysocline was deeper than 4650 m. Increased glacial dissolution appears to result from changes in deep circulation. The CCD during glacial time is interpreted as indicating increased Antarctic Bottom Water flow. The lysocline, on the other hand, may reflect the degree of stagnation of North Atlantic Deep Water.--Modified journal abstract.